Update README.md

Thanks to @nalimilan

README.md

@@ -1,4 +1,12 @@
 openspecfun
 ===========
 
-A collection of special mathematical functions
+Openspecfun provides AMOS and Faddeeva. AMOS (from Netlib) is a
+portable package for Bessel Functions of a Complex Argument and
+Nonnegative Order; it contains subroutines for computing Bessel
+functions and Airy functions. Faddeeva allows computing the
+various error functions of arbitrary complex arguments (Faddeeva
+function, error function, complementary error function, scaled
+complementary error function, imaginary error function, and Dawson function);
+given these, one can also easily compute Voigt functions, Fresnel integrals,
+and similar related functions as well.